ANNUAL MEETING 
127 
forced down and so driven by degrees into the ground, or if the 
wind rises it catches the feather and twists the seed into the 
ground like a corkscrew. 
I have not space to discuss the roots or stem, but should like 
to say a few words about leaves. We all know the endless 
variety they present, and we may be sure that tliere is some 
cause and explanation for every one of these differences. There 
are many interesting problems in this field. Let me just give 
you one or two illustrations. Take for instance the beech. The 
sails of a ship must be proportionate to the strength of the 
masts that carry them. So also the strength of the branches 
determines the leaf area. In our trees the leaves are arranged 
so as to get as much light and heat as possible. In hot dry 
countries they are often arranged so as to cover and protect one 
another, in some of the New Zealand Veronicas for instance. 
With us it is the reverse. Hence the width of the beech leaf 
is determined by the distance between the buds — if they were 
narrower space would be wasted ; if they were wider they 
would overlap. The size and width being thus arrived at the 
length is also determined — if they were shorter they would 
be too small, if they were longer they would overweight the 
branches. 
Now let us take a tree with very different leaves — the Spanish 
chestnut. They are long, narrow, and sword-shaped. Why 
is this ? The terminal branches of the Spanish chestnut are 
much thicker and stronger than those of the beech. Con- 
sequently they can carry more sail. But the distance between 
the buds is but little greater, consequently the leaves cannot 
with advantage be much wider ; but as they must be larger they 
must be long and narrow. Take again the firs and pines. 
Some have long leaves, in others the leaves are short. Why 
is this ? They are, as everyone knows, evergreen, but the 
length of life of the leaves differs greatly. Some keep them on 
for little more than a year, others two or three years, others 
eight or ten, the Pinsapo nearly twenty. And you will find that 
other things being the same, the longer the life the shorter 
the leaf — thus securing about the same leaf surface. To look 
at plants from this point of view makes country life, it seems 
to me, far more interesting. 
Another point in which our conception of plant life has 
undergone considerable modification of late years is as to their 
power of movement. Those who had not studied the question 
used to consider that animals moved, but plants were stationary. 
That is a great mistake. We now know that many of the 
lower plants, especially in young stages, swim about by means 
of fine hairs known as cilia. In fact plants move much more 
than is supposed. I have given instances in which they actually 
throw their seeds to considerable distances. Indeed so far from 
being motionless, it would be more correct to say that they are 
in almost perpetual motion, though the changes of position 
are so slow that they do not attract attention. 
